The Claus process is a well known process for producing elemental sulfur from hydrogen sulfide. As used herein, the Claus process refers to a process in which hydrogen sulfide and sulfur dioxide react to produce elemental sulfur and water. Typically, hydrogen sulfide contained in product gas from petroleum refinery operations is partially combusted in a thermal zone to produce sulfur dioxide, which then reacts with the unburned hydrogen sulfide to yield sulfur and water. The sulfur is then condensed and recovered. One or more catalytic zones are also provided in which the same reaction is further promoted by means of a suitable catalyst, causing additional sulfur to be recovered.
An inherent feature of the process is the presence in the produced liquid sulfur of dissolved hydrogen sulfide, which not only contaminates the product but also poses potential hazards in several areas. In addition to creating nuisance odors in the vicinity of liquid sulfur, hydrogen sulfide may be present in such quantities as to reach toxic levels when loading and unloading the sulfur. Further, when dissolved hydrogen sulfide in liquid sulfur contaminates the vapor space in storage tanks and vessels, there is a threat that the lower explosive limit of hydrogen sulfide will be reached.
To eliminate these problems, a number of methods have been suggested or developed to remove hydrogen sulfide from liquid sulfur produced by the Claus process. Release of dissolved hydrogen sulfide has been carried out by agitating the liquid sulfur by various means, such as by circulating and spraying it, by providing a sulfur lift through air bubbling and by circulating the sulfur over a stripping column. In addition, mechanical agitation has been employed. Released hydrogen sulfide is often removed from the pit gas space by sweep gas, which typically is any suitable inert gas such as air, Claus tail gas or nitrogen.
The means presently known for degasifying liquid sulfur, while effective in varying degrees, often involve expensive installations which are not as efficient as desired and which themselves may cause pollution. It would be desirable to be able to use a simpler method of removing hydrogen sulfide from liquid sulfur which does not cause pollution and is not expensive, and yet is also highly efficient.